Gypsum hardened bodies are used in various applications such as building materials. In recent years, there has been a growing demand for lightweight gypsum hardened bodies with a low specific gravity in order to improve thermal insulation, sound insulation, fire resistance, workability, and ease in handling, for example.
However, the physical strength of a gypsum hardened body is known to decrease as its specific gravity decreases. Also, gypsum panels that include gypsum hardened bodies as their core material are known, such as a gypsum board having base paper arranged on its surface, a gypsum panel using a glass mat as its surface material, and a gypsum panel having glass tissue embedded in its surface, for example. It is known that the strength of such gypsum panels also decreases as the specific gravity of the gypsum hardened bodies used as their core material decreases.
In this respect, methods for strengthening a gypsum hardened body have been contemplated.
For example, Patent Document 1 describes how a specific substituted starch can enhance the core strength of a gypsum wallboard. Further, hydroxyethylated starch is mentioned as an example of such a specific substituted starch.